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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2012-05-17 21:19:46 +0200
committerIngo Molnar <mingo@kernel.org>2012-06-06 16:52:26 +0200
commit7f1b43936f0ecad14770634c021cf4a929aec74d (patch)
treeea200fcf70af41839e049c59a2dc922407e7495b
parent10717dcde10d09f9fcee53a12a4236af1a82b484 (diff)
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op-kernel-dev-7f1b43936f0ecad14770634c021cf4a929aec74d.tar.gz
sched/rt: Fix lockdep annotation within find_lock_lowest_rq()
Roland Dreier reported spurious, hard to trigger lockdep warnings within the scheduler - without any real lockup. This bit gives us the right clue: > [89945.640512] [<ffffffff8103fa1a>] double_lock_balance+0x5a/0x90 > [89945.640568] [<ffffffff8104c546>] push_rt_task+0xc6/0x290 if you look at that code you'll find the double_lock_balance() in question is the one in find_lock_lowest_rq() [yay for inlining]. Now find_lock_lowest_rq() has a bug.. it fails to use double_unlock_balance() in one exit path, if this results in a retry in push_rt_task() we'll call double_lock_balance() again, at which point we'll run into said lockdep confusion. Reported-by: Roland Dreier <roland@kernel.org> Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1337282386.4281.77.camel@twins Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--kernel/sched/rt.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 2a4e8df..573e1ca 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1562,7 +1562,7 @@ static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
task_running(rq, task) ||
!task->on_rq)) {
- raw_spin_unlock(&lowest_rq->lock);
+ double_unlock_balance(rq, lowest_rq);
lowest_rq = NULL;
break;
}
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